To crank start an internal combustion engine, especially a two-stroke engine, the mixture must be enriched. For this purpose, a great many systems are known. Accordingly, a choke flap is mounted in a carburetor upstream of a throttle flap in order to increase the underpressure during crank strokes so that an intense pumping of fuel is effected and thereby the mixture is made rich. In starting devices of this kind, it is problematic that the operator must timely at least partially take the choke flap out of use during run-up of the engine so that an overrich engine and therefore a stalling of the engine associated therewith is avoided.
Japanese patent publication 62060971 discloses that the choke flap of a carburetor automatically opens with the run-up of the engine. For this purpose, the underpressure increasing in the intake channel is used. It has, however, been shown that a system of this kind works too slowly so that a stalling of the engine because of overenrichment can still not be precluded.